Caller Line Identification (CLI) helps the recipient of an incoming communication identify the originator of the communication before the communication is accepted.
An identifier of the originator of the originating terminal is sent from the originating terminal to the destination terminal. The destination terminal then displays the identifier or, if the identifier is associated with a name or alias in the terminal's phone book, displays the associated name or alias instead of the identifier. This latter feature makes CLI more user-friendly.
CLI is now a common feature in telecommunication networks. Mobile cellular telephone networks, the Plain Old Telephone System (POTS) and Voice over Internet Protocol (VoIP) terminal can all support CLI. It make be used with packet switched and also circuit switched communications.
Enterprise workers, especially those working in Sales, Marketing and other functions that might require a lot of one-time contact with individuals, often have to make and receive calls to phone numbers that are not already in the terminal's phonebook.